PITCH AND VOLUME
Sound has two important features. One is pitch. A low-pitched sound is deep, like a roll of thunder or a booming big drum. A high-pitched sound is shrill, like a snake’s hiss or the tinkle of a triangle. Pitch depends on the frequency of sound waves – the number of waves per second. High-pitched sounds have high frequencies.
Some sounds are so high-pitched that our ears cannot detect them. They are known as ultrasounds. Many animals, like dogs and bats, can hear ultrasounds.
The second important feature of sound is its loudness or volume. Some sounds are so quiet that we can only just hear them, like a ticking watch or the rustling of leaves. Other sounds are so loud, like the roar of engines or the powerful music in a disco, that they may damage the ears. Sound volume, or intensity, is measured in units called decibels (dB). Sounds of more than 80-90 decibels can damage our hearing.
An ultrasound scanner beams very high-pitched sound waves into the body. The echoes are analyzed by a computer to form an image, the baby in the womb.
Picture Credit : Google